1. Field of the Invention
The present invention relates to an optical information recording medium, and more specifically to an optical information recording medium that is writable only once by heat mode.
2. Description of the Related Art
With increases in information processing throughput, there is also a strong demand for improvement in recording capacity in the field of optical information recording. A recording pit has been conventionally formed using a light beam having a recording wavelength of 635 nm. However, even higher density is demanded since the start of HDTV (High Definition Television) BS digital broadcasting is near at hand. In particular, an optical disk system that uses a blue-violet laser having a wavelength shorter than 635 nm and a high NA pick-up has been developed and researched, and in ISOM 2000 a DVR-Blue, which uses a blue-violet laser in a phase transition medium, has been developed.
However, there are problems in that when extremely small recording pits are formed using a light beam having a short wavelength, the size and shape of the recording pits formed are irregular, resulting in lowered performance with respect to jitter and noise.
Further, since the DVR-Blue utilizes high NA recording, a distance from a cover layer to a reflective layer is small, whereby if the surface of a reflective layer is rough or if the proportion of relatively high projections in an entire area is high, readability of recording marks is affected, resulting in lowered performance with respect to jitter, noise and the like.